This invention relates to an apparatus for purifying the exhaust gases of internal combustion engines and is of the type which is provided with at least one reactor and a heating burner, both disposed in the exhaust line of the engine.
Exhaust gases of internal combustion engines contain, among others, carbon monoxide, oxides of nitrogen and uncombusted or partially combusted hydrocarbons which contribute to a substantial extent to air pollution.
A known exhaust gas purifying apparatus of the aforeoutlined type (such as disclosed, for example, in German Pat. No. 470,389) utilizes three measures: first, the exhaust gases are mixed with an oxidizing agent, second, the combustion of the gases is initiated by means of an external heat source and third, the aforenamed combustion is continued and maintained by heat which is derived from the burning gases by means of a catalyzer. This known apparatus comprises a combustion chamber into which leads the exhaust conduit of the engine and an air chamber which surrounds the combustion chamber. Upstream of the combustion chamber in the exhaust conduit there is disposed a catalyzer upstream of which there is arranged a spark plug and an injector which, dependent upon the position of associated valves, selectively draws an air-hydrocarbon mixture or preheated air into the exhaust conduit. When the internal combustion engine is started, the catalyzer is heated over the ignited hydrocarbon mixture. After the combustion chamber has reached a certain temperature that is sufficient to bring the temperature of the air in the air chamber to a predetermined value, the admission of the hydrocarbon mixture is interrupted and the preheated air is mixed to the exhaust gas flow. The harmful pollutants of the latter are then converted with the cooperation of the catalyzer while the catalyzer temperature is mantained.
The ever increasing limitations imposed by law on the poisonous components in the exhaust gas of internal combustion engines require the improvements of the aforeoutlined heating system in such a manner that the period in which the necessary operational temperature of the exhaust gas purifying apparatus is reached, is substantially shortened. This is of great significance because, according to the future test methods the emissions are measured from the time of engine start and the test cycles begin to run as early as the start of the internal combustion engine. Thus, during the warm-up run of the engine, even the emission of poisonous exhaust gas components by the heating burner are included in the test results.